Tuning of the Band Gap and Suppression of Metallic phase by Ca doping in La1-xCaxMnO3 Manganite Nano-particles

Abstract Polycrystalline compounds of lanthanum calcium manganite La1-xCaxMnO3, (LCMO) are extensively utilized in energy conversion systems because of their low losses and features related to the transfer of electric charges. This work aimed to examine the impact of different levels of Ca 2+ replacements (x = 0.1, 0.2, and 0.3) on the adjustment of the optical band gap and dielectric losses in La1-xCaxMnO3 nanoparticles. The synthesized samples underwent structural analysis using X-ray diffraction. All generated samples were proven to have an orthorhombic R 3 ̅ c crystal structure. The estimated crystallite size ranged from 25 nm to 32 nm, and other lattice characteristics were also determined. An agglomerated spherical form consisting of nanoparticles with a range of (33-46 nm) can be seen in the scanning electron micrographs of all of the LCMO samples. The nanoparticles had a moderate size distribution and were influenced by narrower grain boundaries. Energy-dispersive X-ray spectroscopy was utilized to verify the elemental makeup of each chemical, while the infrared spectrum revealed bonding in the fingerprint region. A considerable decrease in the optical band gap was detected through the analysis of UV spectrometer absorption data. The band gap exhibited a reduction from 3.95 eV to 3.74 eV. The decrease was determined to be associated with the disparity in refractive index, which was computed using both Moss and Herve-Vandamme equations. Simultaneously, frequency-dependent dielectric study indicated a direct correlation between frequency and the rise in Ca concentration, resulting in an inverse impact on dielectric loss. In addition, the electrical conductivity of these nano-system that were created design as the Ca content grew. This increase was represented by Johnscher's universal power law in the high frequency range.